const int NUM_BTNS = 5;
const int BTN_PINS[] = {12, 11, 10, 9, 8};

int btnState[NUM_BTNS];
int oldBtnState[NUM_BTNS];

void checkButtons()  {
  for (int i = 0; i < NUM_BTNS; i++) {
    // check each button
    btnState[i] = digitalRead(BTN_PINS[i]);
    if (btnState[i] != oldBtnState[i])  { // if it changed
      oldBtnState[i] = btnState[i];       // remember state for next time
      Serial.print("Button ");
      Serial.print(i + 1);
      if (btnState[i] == LOW)  {          // was just pressed
        Serial.println(" pressed.");
      } else {                            // was just released
        Serial.println(" released.");
      }
      delay(20);  // debounce
    }
  }
}

void setup() {
  Serial.begin(9600);
  for (int i = 0; i < NUM_BTNS; i++)  {
    pinMode(BTN_PINS[i], INPUT_PULLUP);
    oldBtnState[i] = HIGH;  // pins idle HIGH
  }
}

void loop() {
  checkButtons();
}